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Monday, December 27, 2010

From the web traffic reports it seems that many people are still on holiday. That makes this a good time to catch up on a number of topics that haven't quite fit in anywhere else.

Hayabusa 2 Approved

John Freeman at the Ancient Solar System blog reports the the Hayabusa 2 mission to sample a near Earth asteroid has been approved for funding by the Japanese government. He reports, that provisional plans for "the next Hayabusa will return samples from a body that has had organic chemistry, interacting with liquid water., in a rocky environment.... those are conditions close to the ones life is thought to have started in, but preserved and uncontaminated by actual life for over 4 billion years. To a guy like me, fascinated by the idea of how chemical systems evolve towards life, that's a mouth watering prospect!" See Breaking news.....Hayabusa 2 lives! (I just recently found Freeman's blog, but have been enjoying reading it. You can see the latest posting on the list of blogs in the right column of this page.)

Tidbits from AGU

My time to pursue future planetary exploration topics at the AGU conference was limited by my real job. For example, I missed NASA night to discuss a possible project in my research field. I did pick up some tidbits in addition to the discussion with the proposing PI for the Journey to Enceladus and Titan (JET). First, I got an explanation of why an Enceladus multiple encounter mission could carry six instruments while a minimal orbiter mission would have to drop both a radar sounder and a narrow angle camera (although it would pick up a magnetometer, which would cost much less than either of the dropped instruments) and still cost almost $200M more. The orbiter would require both a large flight team be funded for several additional years to manage a large number of encounters with moons as the orbit is pumped down and would require a substantial retropropulsion system. Seemingly simple mission options -- a longer flight and a larger propulsion system -- can raise costs substantially.

I also learned that most of the 28 Discovery missions proposed for the current competition would not require ASRGs. Here is the list of missions that I've heard that were proposed that would use ASRGs: Titan Mare Explorer (TIME lake lander), AVIATR Titan plane, Journey to Enceladus and Titan (JET), Io Volcano Observer (IVO), and a lunar lander (that presumably would explore the permanently shadowed polar craters). In addition, the RAVEN Venus radar mapper mission has been proposed, but would be solar powered. NASA has said that the mission with the best science within the cost cap will be the one chosen. (That leaves just 22 mission proposals that I haven't heard about.)

Ryan Anderson is blogging on the planetary science news from AGU at the Martian Chronicles. He's a bit behind, with only two days' reports (of five) so far, but I know what it's like to run a blog and try to complete your PhD at the same time. Check back for his excellent summaries as they appear.

Budget Pressures

A Space News report on NASA night reports that the budget pressures on NASA's planetary science program are creating a difficult financial environment. The major immediate challenges are additional funds required by the Mars Science Laboratory and rising launcher costs. On the latter concern, Jim Green, head of the Planetary Division is quoted as saying, “We are surprised at how extensive those cost increases are,” he said. “You start to wonder where we go from here. How do we get out of low-Earth orbit on a regular basis?” See Rising Costs Cloud Future of NASA Planetary Program for the complete article.

One piece of good news from that article was the proposed FY2011 budget (still unapproved) would fund the first steps to renew production of plutonium essential to power missions to the outer solar system. The article states, “This is really tremendous news,” Green said. “This is very, very, very important to us.” Unfortunately, NASA's FY11 budget is caught up in politics and NASA, like much of the federal government, is being funded through a continuing resolution. That resolution does not allow, or fund NASA to begin any new programs including restarting plutonium production. (The news on the manned spaceflight side is worse, where NASA must continue funding programs that both the President and Congress have decided to cancel.) See Congress freezes NASA's budget until March. It's unclear what budget will eventually appear next spring for the remainder of FY2011 (which ends September 30).

Updates on the Akatsuki Venus Mission

It's now been some time since the Akatsuki spacecraft failed to enter orbit around Venus. For anyone interested in following the investigation, a discussion at the Unmannedspaceflight.com board has been discussing the news as it comes out. See http://www.unmannedspaceflight.com/index.php?showtopic=6508&pid=168732&st=240&#entry168732. Akatuki's problems follows problems with Japan's Nozomi Mars (failed) and Haybusa asteroid missions (ultimately successful after near death experiences). The Japanese space agency JAXA apparently is rethinking its low cost approach to planetary missions and is considering spending more on future missions (possibly with the tradeoff of doing fewer missions). See: Venus Probe's Problems May Cause Japan to Scale Back.

Sunday, December 19, 2010

At the just completed AGU conference, I had a chance to talk with the PI, Christophe Sotin from JPL, for a Discovery proposal to continue the exploration of Enceladus and Titan. The JET proposal would send a small Saturn orbiter to explore those two moons within a constrained ($425M FY10 PI cost), which is substantially less than the estimated costs of the Enceladus missions under consideration by the Decadal Survey (equivalent PI costs of ~>$1.1B FY15 and up depending on option selected). As you may guess, the JET proposal makes some tough choices to fit within the Discovery program -- there's no magic wand.

The biggest compromise is that JET would fly just two instruments: a mid-infrared camera/thermal imager and a mass spectrometer. The most minimal of the proposed Enceladus payloads considered by the Decadal Survey would add a medium angle camera, a magnetometer, and a dust instrument. Other versions of the the Decadal Survey concepts would add up to another nine instruments beyond that minimal list.

Even flying two instruments on JET requires using an already built Rosetta mission mass spectrometer plus other hardware contributed by other nations that wouldn't be counted towards the NASA cost cap. Without those contributions, and with the mission cost estimates shared by the PI, JET would be unable to fit within a Discovery budget. Even adding a simple instrument like a magnetometer would push the JET proposal close to the cost cap, and the PI held firm against what he described as many requests to add an instrument.

Even within these limitations, the JET mission would considerably extend the measurements that the Cassini mission has been able to make in key areas. The JET camera would take advantage of spectral windows in Titan's atmosphere to image the surface at up to 25 m per pixel, 40 times better resolution than the equivalent imager on Cassini and up to 12 times higher resolution than the Cassini radar. The camera would image 15% of Titan in the nominal one year mission at resolutions of 50 m or better The cameras would take images in mid-infrared bands, possibly enabling some compositional studies if the surface materials differ in their mid-IR spectrum. At Enceladus, two of the bands would allow imaging of the distribution of heat sources associated with the tiger stripes and vents at up to 5 m resolution. The higher resolution at both moons would reveal details not seen by Cassini and allow a better understanding of the processes that may have created those structures.

The mass spectrometer would both extend the range of compounds that could be measured by sampling larger molecules and provide greater resolution within ranges of atomic weights. Combined, this mass spectrometer would allow detection of a wider range of organic molecules in the upper atmosphere of Titan and (if present) in the jets of Enceladus.

Here are some examples of the specific studies enabled by JET's instruments from Sotin's poster:

Search for sedimentary layering in Titan valleys resulting from erosion of plateaus and mountains

Map the distribution of solid organics and organics in Titan's small lakes

Measure the energy output and lifetime of Enceladus' jets by high resolution mapping

Determine what molecules (CO, N2, hydrocarbons) make up the mass 28 in Enceladus' plume that has been identified by Cassini

In the nominal one year mission at Saturn, JET would encounter Enceladus several times and encounter both the pro- and anti-Saturn facing sides of Titan on opposite sides of Saturn. This will allow mapping of both hemispheres of Titan while they are illuminated by the sun. For comparison, the Jupiter Europa Orbiter would encounter the Galilean moons on just a single hemisphere of each in its flybys, limiting studies to that hemisphere.

Two extended mission options (which would require additional funding as the prime mission nears its end) would be particularly exciting. JET would be powered by ASRG plutonium power sources, and NASA would like to have a full 14 year test of those power sources. To fulfill that desire, JET would need to continue for approximately seven years after entering Saturn orbit (although further science observations aren't required for the engineering life test). During that time, JET could act as a data relay for any in-situ craft that might land or fly above Titan. This could enhance the data return of a mission such as the Titan Aerial Explorer or AVIATR plane by many times what they could return direct to Earth using their own antennas. Complimentary to this first option (but not required for it), JET could spend three years pumping down its Saturn orbit using Titan flybys and eventually enter orbit around Titan. The orbit could be high, 2500 km, well above the atmosphere and would allow continued observations of Titan's surface for years.

Editorial Thoughts: JET is a good example of the trade offs necessary to conduct Discovery missions in the further reaches of the solar system. Assuming that the Discovery review panel agrees with the PI's cost estimates, Discovery missions to the Saturn system are possible if you can get friends to contribute some hardware and instruments and stick to minimal payloads. JET's two instruments would provide valuable science in key areas of study, though. I would prefer to see one of the more capable Enceladus missions described in the Decadal Survey studies fly over JET -- more instruments are better. (The mass spectrometer and thermal imagers of those missions should fulfill JET's Titan goals.) However, if the Survey doesn't recommend one of those missions, then I believe that JET would be an exciting mission to fly. Better a simple mission than no flight to these worlds in the coming decade.

Thursday, December 16, 2010

Rising Costs Cloud Future of NASA Planetary Program from Space News discusses new pressures on NASA's planetary budget from dramatic increases in the costs of launch vehicles and shorter term pressures from a rise in the costs to complete the Mars Science Laboratory and the lack of a new budget for FY11.

Monday, December 13, 2010

Another blogger has started his own prioritization of missions under consideration by the Decadal Survey. Ray states that he will make his selections based "in the context of our overall exploration and development of space. A mission that helps NASA's human spaceflight program (whether Vision for Space Exploration, Flexible Path to Mars, or other approach) and/or traditional and new commercial space efforts will have an edge in my evaluation."

As I've said in my posts, the goal in presenting my priority list is to use the exercise to provide a way of examining the choices in the hope that a well reasoned argument helps you decide on your own priorities. This other blog starts from a different set of priorities and reaches different conclusions than I have. I encourage you to read his selections.

You can find the blog at Vision Restoration, which appears to primarily focus on manned spaceflight.

This blog entry continues the series to pick the 5 missions that I personally find most compelling for the next decade. I'm under no illusion that I will persuade anyone (especially anyone who influences government spending). However, I find a well argued (and I hope these will be) argument to help me form my own opinions. Please provide your opinions, too, in the comments.

The last several posts have looked at options for exploring those ice-ocean moons. The options range from the Flagship Jupiter Europa orbiter, to a Ganymede orbiter from NASA or ESA, to an Enceladus orbiter (with Titan and other moon flybys), to a Titan lake lander, airplane, or balloon. Writing about these options has been an education for me (and I hope interesting to my readers). In this final entry in this series on ice-ocean moons, I'll look at one way to prioritize these missions.

My ranking of missions is influenced by a senior scientist who has reminded me in emails that you get what you pay for. A mission done too cheaply is one that eventually you'll refly to get the information that was really needed to answer the key questions. With this in mind, here is how I would prioritize the missions:

1) Jupiter Europa Orbiter - A Flagship mission to study Europa and the Jupiter system would return more information, I believe, for the dollar than any other mission choice. However, this choice comes with risks and collateral costs: Assuming that Mars will be the Decadal Survey's highest priority, will there be sufficient funds to fly this mission? Will there be sufficient plutonium to power the spacecraft and would any plutonium remain for other missions? Is the technology mature enough that the risk of major cost overruns is low? I don't have answers to these questions and lack the information to make informed guesses. That's why they pay the Decadal Survey the [metaphorical] big bucks.

2) Either an Enceladus orbiter or a Titan lake lander/submersible: Either mission seeks to explore a constrained set of questions: the cryovolcanic activity and interior of a small moon or the chemistry and properties of an exotic sea.

3) If the Jupiter Europa Orbiter mission doesn't fly, then my third choice would be a Ganymede orbiter that explores that ice-ocean moon in depth and performs several flybys of Callisto. I also hope -- although the mission concept study did not address this possibility -- that this mission would also make several flybys of Europa to further our knowledge of its interior and surface.

4) Either an airplane or balloon to explore the atmosphere and remotely observe the surface of Titan in detail. Placing these options last was a hard call. From the personal arm chair explorer perspective, I would pick either the Titan airplane or balloon as my first choice. I want to see the surface up close and personal as if I was flying above it. However, both missions would suffer from severe limitations on the information they could return to Earth without an orbital relay spacecraft. If either flies, I suspect that we'll eventually refly the mission when a capable orbiter is also sent to Saturn or Titan to enable high bandwidth data return and in-depth coverage of many locations rather than a few. (However, the Galileo mission with its crippled antenna showed how much science can be done with limited bandwidth -- these would be good missions without the data relay.)

These choices assume that all missions have an equal chance of being selected. In reality, each faces significant challenges on the path to selection. Each must fit within an available budget and beat out tough competition to be selected. If any of these missions surmounts these obstacles, then any would be an excellent choice.

In a perfect world, several of these missions could fly, funded from different NASA and ESA budgets. NASA might fund a Flagship Jupiter Europa Orbiter and a small Enceladus flyby or orbiter mission that also acts as a data relay for an ESA Titan balloon mission while a Titan lake lander is funded from NASA's Discovery program. An ESA Ganymede orbiter would also explore that world. In our less than perfect real world, I would be happy to see at least one and, if all gods smile, two of these missions fly. Which one or two will be the result of hard looks at budgets and winning out over tough competition from other excellent missions.

Tuesday, December 7, 2010

We occasionally are reminded just how hard planetary exploration is. I have just read the news that the Japanese Akatsuki failed to enter Venus orbit. So many things must go right in a mission. Many missions have had that moment where they didn't. Most were able to recover and continue. A few were not so fortunate. We'll have to wait to see what can be salvaged for the Akatsuki mission.

Sunday, December 5, 2010

Last October, I was fortunate to receive a preview of the Decadal Survey's Titan lake lander mission concept study. At that time, I published what proved to be one of the most popular entries in this blog, Titan Lake Probe Mission Concepts.

In this entry, I'll provide some additional background on information provided by the report that wasn't in the conference presentation that the earlier entry was based on. To recap that earlier summary, the study looked at four variations of Titan lake landers that would approximately fit within the FY15 budget for a New Frontier's class mission. The study looked at various combinations of probes that would float on a Titan lake surface or would descend to the lake bottom, carry out measurements, and resurface to relay the results. Two of the options provided long-lived plutonium-based power systems on the floater to allow a long period of study from the lake surface. Another option had a battery powered floater, and the final option had a battery-powered submersible. (One Flagship-class option combined a long-lived floater and a battery-powered submersible.) All options would study the atmosphere during the descent to the lake.

SGa: Atmospheric evolution (studied during descent through the atmosphere and by analyzing the lake)

SGb: Lake and atmospheric interaction to determine how the two exchange material much as the Earth's hydrosphere and atmosphere influence each other (studied by a long-lived floater on the surface of a lake)

SGc: Lake chemistry (studied by either a floater or a submersible)

SGd: Interior structure (studied by a long-lived submersible on the lake bottom to determine whether or not there is a large ocean deep beneath the surface as there is at Ganymede and Europa)

For me, the most interesting new information in the complete mission concept report was the cost estimates for the different options. The estimates range from $1.3B (FY15 $s) to $1.5B. (And I'll quote the verbiage on estimates from the report: "Cost estimates described or summarized in this document were generated as part of a preliminary concept study, are model-based, assume a JPL in-house build, and do not constitute a commitment on the part of JPL or Caltech." In other words, these are preliminary estimates useful for evaluating concepts. Cost estimates for an actual mission probably would differ.)

I was surprised at the relatively small difference -- ~14% -- in estimated costs between the short-lived floater with just three instruments and long-lived floater with ten instruments. Or for about the same amount as the long-lived floater, a short-lived submersible could provide slightly greater relative science return. In the initial studies of the Europa and Titan Flagship missions, costs were initially held to a predetermined figure. Later, the concept teams were allowed to define the science sweet spot where the cost-benefit curve provided maximum return. It appears that there may be a similar case for spending another ~15% above the minimum mission to return significantly more science.

The Flagship option is a bit of ringer in the list of mission concepts. To be able to provide both a long-lived floater and a very capable submersible, the concept presumes that a Flagship-class orbiter mission bears most of the costs of launch and mission operations. A stand alone floater/submersible mission presumably would cost significantly more. However, both the short-live submersible and the long-lived floater as stand alone missions would provide much of the science benefit of the Flagship option within the cost ranges being studied.

For comparison, I included the proposed Discovery-class long-lived floater TiME mission that is competing for launch in the current Discovery selection. I don't know what the equivalent cost of an FY15 $ Discovery mission is, but in FY10 $s, the PI cost must be kept to $425M, not including launch vehicle and the plutonium ASRG power supply. I attempted a back-of-the-envelope comparison of the short-lived floater mission concept and the TiME mission. After accounting for inflation, differences in reserve allowances, and possible launch vehicle differences, I was able to get to within $100-150M of an FY10 Discovery mission. The TiME mission is being designed to Discovery costs by a very capable team. Getting to this small of a difference makes me hopeful that the TiME mission can be implemented within a Discovery budget. If it can, it would implement an in-between option not considered by the concept team: a long-lived floater with a constrained instrument payload. I believe this would be a dynamite mission, especially at the cost of a Discovery mission.

About Me

You can contact me at futureplanets1@gmail.com with any questions or comments.
I have followed planetary exploration since I opened my newspaper in 1976 and saw the first photo from the surface of Mars. The challenges of conceiving and designing planetary missions has always fascinated me. I don't have any formal tie to NASA or planetary exploration (although I use data from NASA's Earth science missions in my professional work as an ecologist).
Corrections and additions always welcome.